I don't think there have been any studies to say one way or another. There has been at least one study on the effect of neem oil on earthworms. For unknown reasons it increased their population.

This assumes neem oil was used and not some pesticide with an extract from neem oil in which case the 'inert' ingredients are almost certainly far more toxic to soil life than the neem oil itself..

Beneficial nematodes require soil temperatures above 55F to be effective so waiting until almost the beginning of October to apply them is risky. You'll either need to take your chances with the Neem or wait until the soil warms sufficiently next spring before applying the nematodes.

FWIW, resources indicate Neem (azadirachtin) biodegrades in the soil in a matter of a few weeks. JaG's comments regarding additives/surfactants would still apply.

Thanks everyone. It was clarified oil of Neem - nothing else in it. I am going to try the nematodes in early September while it is still hot. Gotta get those cuke beetles and squash vine borer grubs - don't want them coming back inside my mosquito net cover for the raised bed.

DL

I am not 100% positive but I don't believe that pouring anything on/in the soil will effect either of the pests you mention.

I stand corrected and learned something new.